Pigeons demonxtrate sex determinaation such that a genotype produces a male and a genotype produces a female. The gene for feather colort is located on the chromosome, and the red allele is dominant over the brown allele. Three crosses between brown male pigeons and red female pigeons were performed, and the results are shown below.
Which of the following is the mean number of male offspring produced by the three crosses?
a. 27
b.20
c.11
d. 9